Ramjet device



D. H. SLOAN RAMJET DEVICE April 25, 196] 5 Sheets-Sheet 1 Filed Jan. 26, 1951 FIG.I

BURNING MIXTURE //II V ISSILE WALL IGNITION LEAD FIG.5

ATTORNEY WNW E0 M w mm April 25, 1961 Filed Jan. 26, 1951 D. H. SLOAN RAMJET DEVICE FIG.6

3 Sheets-Sheet 2 MISSILE WALL INVENTOR.

DAVID H. SLOAN A TTORNEY D. H. SLOAN RAMJET DEVICE April 25, 1961 5 Sheets-Sheet 3 Filed Jan. 26, 1951 INVENTOR.

DAVID H. SLOAN Y B jzwflm ATTORNEY 2,981,065 RAMJET'DEVICE David H. Sloan, Berkeley, Calif., assignor to the United States of America as represented by the Secretary of the Navy Filed Jan. 26, 1951, Ser. No. 207,943 4 Claims. (Cl. 60-3952) The present invention relates generally to a ramjet device, and more particularly'to a"duc"ted combustion system for maintaining burningin the combustion chamber of a ramjet missile.- T

The present invention relates to an improved burning system for use in rarnjet guided missiles of the general type disclosed in US; patent application, Serial Number 659,188, filed April 3, 1946, now Patent No. 2,892,410, D. H. Sloan and W. A. Goss, inventors.

In the construction and utilization of ramjet devices considerable difficulty has been experienced in obtaining proper'burning of the fuel. In particular, difliculty has been encountered because of so-called rough burning which frequently terminates in flash-backs or blowouts. Also, in flame holders of the types hereintofore used, optimum burning of the fuel has frequently not been accomplished. This is because of the fact that fuelflows through the combustion chamber too rapidly and may not. become ignited or may be ignited for short explosive bursts of flame followed by intervals of no flame.

This condition results from the fact that a simple baffle-like flame holder as heretofore used, while providing a protected region in which to stabilize or anchor at small flame as well as operating for spreading flame to the air fuel mixture by disturbance of the flow pattern in its wake, constitutes at best only a compromise because the requirements fora satisfactory baffle are contractory, i.e., optimum stability of burning and best mixing and spreading of the burning fuel mixture cannot be-satisfactorily achieved by a simple baffle.

In accordance with the present invention, a duct has been placed in the air-fuel stream of the combustion chamber. This duct provides a plurality of separate fuel channels, and in at least one of 'these channels conditions are maintained such that burning of a small portion of the fuel is carried forward with a maximum degree of protection and resultant stability. To this" end, there has been provided a restriction to produce a jet effect which in turn, reduces the quantity of air-fuel mixture passing through the duct and causes the maintenance of an area of low velocity, high turbulent fuel mixture, and which ignites the fuel mixture Within this low velocity, high turbulent area. The burning of the small quantity of fuel communicates itself to an air-fuel stream within the protected area so that substantially complete combustion of the fuel in the duct takes place. The combusted fuel issuing from the protected duct is mixed with the fuel flowing past the 'duct spreaders are utilized to insure rapid mixing of the combusted and uncombusted fuel mixtures at the inter-face between the two streams.

The burning within the duct further heats at least a portion of the burner above the ignition point of the mixture so that ignition of the fuel stream becomes spontaneous after a brief ignition interval. The burning with in the duct heats the duct wall and communicates a large amount of heat to the fuel stream to provide material preheating of the fuel prior to the junction of the streams jet missiles.

Patented Apr. 25, 1961 of combusted and non-combusted downstream from the duct.

One of the foremost objects of the present invention, therefore, is to provide an improved ignition unit for ram- It is another object of the invention to provide a ducted ignition device which effects separation of the functions of burning stabilization and flame mixing and spreading.

A further object of the invention to provide a unit securing progressive burning of the fuel in a ram'jet device.

It is a further object of the invention to provide an ignition system in which stability is fostered in the combustion phase within the unit while mixing is accomplished by suitable mixing devices in the precise amount desired and at the most effective location, i.e., at the interface between the combusted stream issuingfromthe ignition unit and the main fuel stream or streams flowing past said unit.

Even another object of the invention to provide, in a ramjet missile, an ignition unit which constitutes both a protected region in which to stabilize a flame as well as agitating means for spreading the flame in the air-fuel mixture flowing past the unit by the disturbance of a fluid flow pattern arising in the wake of'saicl unit in order to obtain optimum fuel combustion.

1 And another object of the invention to provide a ducted combustionsystern having a plurality of progressively ignited fuel-carrying channels.

Still a further object of the invention toprovide a ducted combustion chamber in which portions of the fuel are sequentially ignited in progressively turbulent conditions.

Other objects and many of the attendant advantages of this invention will be readily appreciated as the same becomes understood by reference to the following detailed description when considered in connection with the accompanying drawings wherein:

Figure 1 is a diagrammatic view of a section of a ramjet device utilizing as an ignition unit a conventional flare heretofore in general use in this type of device;

Fig. 2 is a view similar to'Fig. 1 but showing the use of an ignition baflle' as a flame stabilizing device;

Fig. 3 is a diagrammatic view of an improved ignition unit according to the present invention;

Fig. 4 is a similar diagrammatic view of a modification of the improved ignition unit;

Fig. 5 is a further diagrammatic view of another embodiment of the invention;

Fig.' 6'is a diagrammatic view of a further modification to accomplish the objects of the invention;

Fig. 7 is a similar view showing the application of the device to a three-stage combustor;

Fig. 8 is a perspective view partially broken away of a modification of the invention for application to a larger type of ramjet device;

Fig. 9 is a similar view showing utilization of tandem type combustors; and

Fig. 10 is a perspective view, also partially broken away, of an annular type combustor according to the invention.

In the exemplary embodiments according to the present invention, Fig. l discloses a well known flare type of combustion initiator in which a pyrotechnic flare 10 is placed within the combustion chamber 11 in the fuel-air mixture stream; Plate 10 is ignited by any suitable means, usually by an electric igniter device '12. The presence of the flare 10 produces a turbulence in the airfuel mixture stream which causes at least a portion of the air-fuel mixture to trail behind the igniter unit" that the flare 10 communicates flame to the mixture and causes burning of the mixture flowing downstream from the flare 10.

embodying the essence of the present invention.

3 -It has also been proposed to utilize a flame holding baflle 14 as shown in Fig. 2, the baffle being intended to cause a low velocity area back of the baflle inwhich a fuel mixture can be ignited by suitable means, suchas an electric spark 15 or a heated element.

As pointed out hereinbefore, these device have not been entirely satisfactory in that the proper mixing of the burning gases with the main fuel stream has not always resulted. Accordingly some of the fuel hasfrequently remained unburned or the fuel has had uneven or rough burning, so that optimum burning seldom has taken place.

In Figs. 3 to 6, inclusive, there are shown in diagrammatic form several modifications of a ducted combustor 7 These modifications disclose a few of the configurations that may be utilized to provide a controlled protected area within a portion of the fuel stream where the conditions, necessary for absolute certainty of maintenance of combustion, are maintained and properly propagated to the main body of the fuel stream.

In Fig. 3, a diagrammatic or schematic exemplification of the present invention is illustrated. The rear interior of the ramjet device 13 defines a combustion chamber 11 through which the air-fuel mixture streams at high velocity. Within this chamber 11 aduct-like passage 16 has been placed preferably coaxial with the combustion chamber 11 and having a constriction 17 adjacent to the forward-end of the duct 16 so that only a small quantity of fuel can enter through the jet-like orifice 13. Within the duct 16 there is placed a flame holding baflie 19 behind which is a suitable ignition device 15. Usually a flame spreader or gutter 20 is appiled to the trailing edge of the duct 16 to impart turbulence to the fuel streams and expedite the commingling of the streams at the interface of the combusted and non-combusted. fuel downstream from the duct 16.

In the modification according to Fig. 4, there is shown a substantial open-ended duct 21 in which a burner 22 has a flared skirt 23 to provide a low area jet 24 to produce a stagnation effect of a portion of the fuel mixture behind the burner 22.

In the modification according to Fig. 5, the constrictcd nose 25 of the duct body 16 has been shaped to provide vane-like jet portions 27 which give a whirling motion to the small quantity of fuel entering into the duct to.

In the modification according to Fig. 6, the nose 28 of the duct 16 has been given a re-entrant jet opening to provide an annular baffle maintaining a substantially annular pool of the fuel-air mixture.

In the practical construction, of devices according to the present invention, that portion of the body 13 of the ramjet which defines the combustion chamber 11 has installed therein one or more ducts 21 which are firmly anchored, as by struts 35, tothe inner wall of the combustion chamber it. These duct devices 21 produce a plurality of fuel channels A, B, etc., which are substantially separated from each other by the thickness of the duct walls. A suitable burner 22 is placed within one, preferably the innermost, of these channels. For example, in Fig. 4, there is shown a flare type burner 22 having an expanded skirt portion 24 which, in cooperation with the inner wall of the duct 21, provides an annular jet opening 24A which reduced the quantity of fuel mixture flowing through channel A of the duct 21 and which causes a small portion of the fuel to linger behind the flare 22.

In operation, the burner 22 will be started by any suita ble means, such as an electric igniter 12, after which the flare 22 will communicate the flame to the portion of the fuel mixture lingering behind the burner 22 and that in turn will propagate flame to the fuel mixture within the duct 21. The'burning of the fuel mixture within the duct 21 will bring parts of the duct 21 and burner 22 mination of the second or outermost duct 32.

to a temperature suflicient to produce spontaneous ignition of the fuel mixture passing through so that, in theory at least, it is unnecessary to maintain the operation of the burner 22 beyond this pro-heating period.

A further desirable effect is obtained in that the hot walls of the duct 21 communicate a large amount of heat to the fuel mixture in the adjacent channel B so that when the partially combusted material within the duct mingles with the pre-heated fuel mixture in the surrounding chamber B, ignition or flame propagation to the adjacent channel B is considerably expedited.

It frequently may be desirable to maintain a combustion chamber utilizing a plurality of sequentially ignited fuel channels. For example, in Fig. 7, there is shown a pair of ducts 31-32 which, together with the inner wall of the combustion chamber 11, define two main fuel mixture channels B--C together with the centrally located ignition channel A. It is usually desirable to construct the ducts 3132 of varying length, preferably increasing in length in the direction away from the igniter channel A. That is, with a centrally located ignition element 33 the innermost duct 31 will be shorter than the outermost ducts 32, so that the ignition points progress away from the igniter element 33 as the flame is propagated downstream from the igniter 33. In a combustor of this type, the flame will be initiated behind the burner or. flame holder 34 in the portion of the mixture which is retained behind the burner 34 because of the reduced jet opening. The fuel mixture passing through alongside of the igniter 33 will then be combusted, and at the end of the inner channel A will be spread out so as to mingle with the non-combusted fuel in the next adjacent channel B, which will mix at its inter-face and combust the fuel in the intermediate channel before the ter- Preferably the outermost duct 32 is provided at or adjacent its terminal end with a restriction or flame spreader 36 which causes rapid intermingling of the combusted fuel in the intermediate channel B through the inter-face with the fuel coming through the outmost channel C. The restriction 36 of the intermediate channel B not only serves as a flame spreader but also creates an increased pressure facilitating flame propagation in the intermediate channel B. In this manner the various portions of the fuel are sequentially ignited and are thoroughly mixed so that substantially constant and complete fuel burning is secured.

Many types of igniter elements may be utilized in any of the various embodiments of the present invention. For example, in Fig. 4 the pyrotechnic flare type of burner 22 is shown, while in Fig. 7 there is disclosed a bleeder type burner 33 in which a small quantity of fuel mixture is withdrawn from the main fuel stream and introduced into the burner cavity where it is ignited by any suitable means, such as an electric spark 15. Instead of introducing a portion of the fuel mixture a special fuel may be piped into the burners from an auxiliary source as shown in Figs. 5 and 9. Obviously the type of burner utilized in any particular combustor will be determined by the exigencies of the occasion.

Sometimes it is found desirable to provide a plurality of sequentially operating igniters so that if for any reason unequal or burst type combustion should occur at one of the burners, another burner will be available to maintain combustion in spite of this undesirable operation. Accordingly, in Fig. 9, there is shown a plurality of sequentially arranged ducts 4t) and 41 each of which is provided with a burner 42 and a jet-like passage 43 for retaining flame behind the burner 42 so that, in the event either of the burners 42 should fail to operate either momentarily or permanently for any reason, the other burner 42 will maintain the operation of the device in spite of the failure of one of the burners 42 therein. The multiple burners 42 are preferably provided with a fuelusually gaseous-from an auxiliary source, not

shown, of sufficient capacity to supply a supporting flame until the parts have been heated to the point where automatic ignition takes place.

While a simple duct system having one or more concentric ducts, according to the present invention, is quite satisfactory in the smaller missiles, it is-found desirable in the larger missiles to provide a plurality of burners or ducts acting in parallel. For this purpose I have shown, in Fig. 8, a plurality of parallel operating ducts 50 arranged in annular formation and supported by means of an annular frame 511 secured Within the combustion chamber 11. Each of the ducts 50 which may be of a plurality of stages contains at least one duct member and preferably more, the innermost duct being provided with a burner 52 substantially as described in connection with the preceding figures.

In the operation of this multiple parallel unit each of the burners 52 will be ignited and propagate flame to the immediate surrounding duct; also the ducts 50 define a fairly large space between the ducts and the wall through which the fuel mixture flows. Because of the configuration, rapid mixing of combusted and heated uncombusted fuel occurs at the trailing end of the ducts 50 and develops very complete utilization of the fuel.

In the intermediate size devices it is found that an annular type duct is more satisfactory and simpler to build than a plurality of parallel operating ducts 50. In this modification according to Fig. there is shown a plurality of substantially concentric duct-like members 5556 defining a plurality of annular channels about an inner tubular member 57 through which usually no fuel or other material is expected to pass. A shroud-like member 58 of annular formation is provided which substantially closes an inner annular channel so that a small quantity of the fuel mixture may pass behind the shroud into a protected area 59 in which a plurality of igniter devices 60 may be installed. The shroud 58 likewise cooperates with the next adjacent duct 55 to provide an. annular jet-like opening 61 through which a quantity of fuel passes to produce a stagnant or pool-like area behind the shroud 58 where burning can be maintained under the most favorable conditions. The intermediate duct 55 then operates to provide a plurality of channels A,B'-C' so that at the trailing edge of the intermediate duct 55 the combusted material from the inner channel A is mixed with and ignites the mass of fuel mixture in the intermediate channel B and the likewise combusted material from the intermediate channel B intermingles with and combusts the material in the exterior,

or outermost channel C; preferably this annular second channel is provided with suitable restrictions 62-63 to produce the desired high pressure within the intermediate channel B and extreme turbulence in the downstream portion of the commingled fuel streams.

Obviously many modifications and variations of the present invention are possible in the light of the above teachings. It is therefore to be understood that within 6 l the scope of the appended claims the invention may be practiced otherwise than specifically described.

What is claimed is:

1. In an aerial missile of the ramjet type, a combustion chamber for the passage of an air-fuel mixtureincluding an inner cylindrical member mounted in said chamber in the longitudinal direction of said missile, a plurality of substantially concentric duct-like members defining a plurality of annular chambers about said inner cylindrical member, said duct-like members terminating in axially spaced relationship to propagate flame successively to adjacent chambers, a shroud-like member in one of said duct-like members which substantially closes said one duct-like member so that a small quantity of said air-fuel mixture may pass behind said shroud into a protected area in said one duct-like member, at least one igniter in said protected area of said one duct-like member to ignite the airfuel mixture contained in said protected area therein, the combustion of said air-fuel mixture in said shrouded duct-like member heating the duct wall thereof to communicate heat to the air-fuel mixture in the adjacent chamber, and means in the downstream end of said combustion chamber and located between said inner cylindrical member and the end of the duct-like member which terminates the furtherest downstream to restrict the flow of the air-fuel mixture and products of combustion in order to produce high pressure in the upstream chambers and extreme turbulence in the downstream portion of the commingled air-fuel streams.

2. An arrangement as recited in claim 1, wherein said shroud-like member is of annular formation.

3. An arrangement as recited in claim 2, wherein said last mentioned means comprises an annular convergentcylindrical shaped nozzle arrangement.

4-. An arrangement as set forth in claim 1, wherein a plurality of igniters are provided in said protected area of said one duct-like member to ignite the air-fuel mixture.

References Cited in the file of this patent UNITED STATES PATENTS France Nov. 10, 1942 

